Compiler Optimization Behavior: Short Circuiting

main.c

#include <stdio.h>
#include <stdlib.h>

struct Reeds {
    int store;
};

int main(void) {
    struct Reeds* r = NULL;
    // r = malloc(sizeof(struct Reeds));
    printf("%d\n", r->store == 0 && r != NULL);

    return 0;
}

/*
 * Running with `-O1` seems to run the null check before accessing the
 * struct member (swap the sides of the boolean expression).
 *
 * (This behavior might already be listed in the docs of the `O` flag.)
 *
 * Command outputs:
 *
 * $ gcc -O1 main.c && ./a.out
 * 0
 *
 * $ gcc -O0 main.c && ./a.out
 * zsh: segmentation fault  ./a.out
 *
 *
 * $ clang -O1 main.c && ./a.out
 * 0
 *
 * $ clang -O0 main.c && ./a.out
 * zsh: segmentation fault  ./a.out
 *
 */